Many electronic timepieces each of which has a solar cell and utilizes a light such as a sunlight as a power generation source have been conventionally commercialized. In these electronic timepieces, when a solar cell is arranged under a light semi-permeable dial, a design of the dial is restricted, and commodities with various designs cannot be proposed.
That is, since the surface of the solar cell has a dark brown color, the dial must be arranged on the solar cell in order to hide this color of the surface. On the other hand, in order to generate the power upon receiving a light at the solar cell, properties which transmit a light to some extent, i.e., the light permeability is required. Therefore, using a white color to the dial results in the dial having an off-white color tone like frosted glass, and a beautiful white color cannot be obtained, thereby restricting the design.
Meanwhile, a reduction in power consumption of timepieces has advanced in recent years, and each timepiece can be driven even if an area of a solar cell is decreased to some extent. Thus, an electronic timepiece with a solar cell in which a solar cell is arranged on an outer periphery substantially vertically with respect to the dial has been proposed. Such a prior art is disclosed in Japanese Utility Model Application Laid-open No. 42390-1987 (Patent Reference 1) or Japanese Patent Application Laid-open No. 2002-148366 (Patent Reference 2). There is a timepiece in which a solar cell formed on a strip-like printed board having the flexibility is wound on a wall surface of a gap portion between a windshield and a dial.
FIGS. 17 to 20 show an embodiment described in Patent Reference 1, in which FIGS. 17 and 18 show a first embodiment and FIGS. 19 and 20 show a second embodiment.
A solar cell block 121 shown in FIG. 18 has a configuration in which a plurality of solar cells 123 are mounted on a flexible printed board 122, these solar cells 123 are connected with each other through an electrode pattern and spacers 124 are arrange to fill gaps between the solar cells 123. A solar cell block 121 is bonded to a support ring 125 through the flexible printed board.
FIG. 18 is a cross-sectional view of a wrist watch showing a state in which the solar cell block 121 depicted in FIG. 19 is assembled in a watch case 127. In the solar cell block 121, the surface of each solar cell 123 is erected with respect to a dial 126 and faces the center of the watch. This solar cell block 121 is configured to be attached to the support ring 125.
A solar cell block 131 shown in FIG. 21 is obtained by forming solar cells 133 each consisting of amorphous silicon on a stainless sheet 132 on which an insulating film is applied. The plurality of solar cells 133 are connected with each other through positive and negative electrodes 134a and 134b arranged at both ends of the stainless sheet 132 and a wiring pattern 135.
FIG. 20 is a cross-sectional view of a wrist watch showing a state in which the solar cell block 131 depicted in FIG. 21 is assembled in a watch case 136. The solar cell block 131 formed of a flexible stainless sheet is wound on the inner side of a facing inner wall surface 137 of the watch case 136, and the solar cell block 131 is arranged in such a manner that the solar cells 133 are erected with respect to the dial 138 and face the center of the watch.
FIGS. 22 and 23 show the first embodiment described in Patent Reference 2.
FIG. 22 is a plan view of an elongated strip-like solar cell 141 formed on a substrate 140 having the flexibility, and positive and negative electrodes 147a and 147b are arranged at both ends of the solar cell 141.
FIG. 23 is a cross-sectional view showing a state in which a solar cell 141 is assembled in a watch case 146. As to the solar cell 141-in FIG. 23, there is shown a cross-sectional view taken along a D-D line in FIG. 22 and a part where the positive/negative electrode 147a (147b) of the solar cell 141 is in contact with a connection spring 148. The solar cell 141 is arranged on an inner peripheral surface 144a of an annular banking portion 144 along an outer peripheral portion of a timepiece movement 142 above an arrangement surface 142a of a dial 143 of the timepiece movement 142. This solar cell 141 is assembled in a watch case 146 with a facing ring 145 having the light permeability being arranged on the inner side.
However, in the configuration according to the first embodiment of Parent Reference 1 shown in FIG. 18, the plurality of solar cells 123 are circularly arranged, electrically connected in series and have a fixed length. Therefore, when the same solar cell block 121 as this embodiment is assembled in a timepiece having a small panel cover diameter, a light is not applied to some solar cells 123 because the solar cells 123 overlap each other. However, the solar cell block 121 has a problem that the necessary power cannot be obtained since the output power from the solar cells 123 on which a light is not applied restricts the entire output power.
Likewise, since the solar cells 133 are electrically connected in series, the second embodiment of Patent Reference 1 shown in FIG. 20 has the same problem as the first embodiment of Patent Reference 1 shown in FIG. 18.
Further, in case of the solar cell block 131 of the second embodiment of Patent Reference 1, since the positive and negative electrodes 134a and 134b for fetching the generated power are provided at both ends of the solar cell block 131, there is a problem that the positive and negative electrodes 134a and 134b overlap each other and hence the power cannot be fetched when this solar cell block 131 is used in a timepiece having a small panel cover diameter.
Likewise, the first embodiment of Patent Reference 2 shown in FIGS. 22 and 23 has the same problem as the second embodiment of Patent Reference 1 since the positive and negative electrodes 147a and 147b for fetching the generated power are provided at both ends.
It is to be noted that the panel cover diameter means a diameter of a shape in a plane direction in a space in which hour/minute/second hands are arranged between a dial and a windshield, and it means an internal diameter of a facing ring in case of a timepiece having the facing ring formed therein.
Furthermore, in the configuration of the first embodiment of Patent Reference 2, since the annular banking portion 144 on which the solar cell 141 is arranged is formed on a timepiece movement component, there is a problem that the timepiece movement component on which the solar cell is arranged must be changed in case of varying a panel cover diameter.
It is to be noted that reducing the internal diameter of the facing ring 145 alone to increase a width W of the facing ring 145 can be considered in case of a timepiece having a small panel cover diameter, but a timepiece having a large external diameter of the timepiece case 146 with respect to the panel cover diameter is obtained, resulting in a design problem.
As described above, the prior art has a problem that the solar cell or the timepiece movement component on which the solar cell is arranged cannot be used in common in a timepiece having a different panel cover diameter, and that the solar cell, the solar cell block and the watch movement component on which such members are arranged must be newly recreated in accordance with a panel cover diameter.
It is, therefore, an object of the present invention to provide, in an electronic timepiece with a solar cell in which the solar cell is arranged substantially vertically to a dial, an electronic timepiece with a solar cell having a configuration in which a common solar cell and a common timepiece movement can be used irrespective of a panel cover diameter size.